Heatwaves, cyclones in national forecast

Between heatwaves and possible floods, fires and cyclones. There's little good news in the national weather forecast for the final days of 2018.

The mixed bag of predictions is set to see temperatures soar well above average and rainfall records continue to tumble.

Queenslanders could soon be bracing for the first cyclone of the season, as a monsoon trough develops over the north of the continent.

The state is set to see the most variety in conditions with pre-New Year's Eve temperatures, ranging from a balmy 32C and sea breezes on the Gold and Sunshine coasts, warming to 38C around Gatton, Toowoomba and Warwick.

Those west and north west of Darling Downs will want their air conditioners at the ready as temperatures reach in excess of 40C, and the Bureau of Meteorology has warned no real sign of relief is in sight.

December monthly rainfall records have already been shattered in the far north, but more "significant falls" are expected in coming days, prompting a major flood warning for the Daintree River and flood watches for the Mossman, Mulgrave and Russell rivers.

Poor air quality is set to be an issue in Sydney on Thursday when temperatures range between 29C in the city's east and 39C in the west.

Severe heatwave conditions are on the cards for the state's south east, while the mercury is expected to reach 41C in the central west and 44C in the Riverina.

Much of southern Australia can expect temperatures 10-14C higher than usual for this time of year, the Bureau of Meteorology predicts.

By midday on Thursday, the temperature had already reached a whopping 44.5C at Port Augusta, in central South Australia.

Extreme temperatures sweeping across Victoria could keep emergency services on their toes.

Hot, dry conditions mean severe fire danger warnings are in place for the Mallee, Wimmera and northern country districts, including Mildura, Swan Hill, Kerang and Echuca where the temperature could reach 44C.

As well as total fire bans in some regions, health warnings are also in place for pregnant woman, children, the elderly and people with medical conditions.

"Consider reaching out to someone you know that may be suffering in the heat today," the state's health department warned.